Boiler



H. C. DAVIS Dec. 4, 1934.

BOILER Filed July 8, 1953 INVENTOR. Howard C. fla 1015 BY v ATTORNEY Patented Dec. 4, 1934 UNITED STATES .My invention relates to steamboilers and in particular to low pressure steam boilers especially suitable for residential heating systems.

The capacity and efliciency of a steam boiler;

depend, to a certain extent, upon the heat transfer surface of the boiler. The usual low pressure steam boiler suitable for residential heating sys-, terns is made of cast iron and the heat transfer surface consists of the crownsheet of the boiler and the flue gas passage through the boiler. While a flue tubeboiler is generally much more eflicient-than the usual cast iron boiler, flue tube boilers have not heretofore been generally available in'boilers of a size and capacity required in the'low pressure boiler commonly used in residential heating systems because of the expense of manufacture and the inaccessibility of the tubes for repair and replacement. Like the cast iron boiler, the heattransfer surface of the flue tube boiler heretofore available is a constant factor which can not be varied. This condition necess-r, itates; aseparate designfor eachboiler capacitydesired. Each separate design requires different tools and molds so that the economy of multiple production is only availableHto the boiler manufacturer in so far as it can be attainedwithin classes as defined by ratedcapac-ity. I By my, invention 1, am enabled toproduce steam boiler of a design which-makes it comparatively inexpensive to manufacture and also obtain the economical advantage in manufacture incident upon having a particular boiler design suitable for severaljdifferent capacity ratings. The:

heat transfer surface of the boiler ofmy inven-.

tion can be readily varied to vary the capacity of the boiler. Thus, with one-design of boiler, there can be'producedboilers of, several different capacities; In accordance with my invention, I construct a boiler havingtwo'sections, a-combus: -40 tionchamber and a, water compartmentp Ihe casing of the boiler, has an opening through that portion-of the wall thereof which forms the wall of; thecombustion chamber. In this opening in the-wallof the boiler, there is mounted aremovable heat exchanger which is suitably connected to the water compartment of the boiler. The

constructionis such lthatgseveral heat exchangers,

each-, havinga different heat transferareacan be mounted ,in theboiler. By removing the heat exchanger mounted inthe boiler andreplacingit withtan exchanger having a different area, of heattranstersurface, the capacity *of' the boiler can be varied within the limits 'which variations ofzthearea of" the-heat exchange surface will 155 p rmit variatlonsin' apacitr.

Specifically; .in one form of boiler whichembodies my invention, the heat exchanger. is of. the hue tube type. For example, in a boiler of, small capacity, suitable for the ordinary home, the, boiler is preferably of the upright type. The. 0 boiler proper is'madeup of two cylindricalsteel shel1s,one within the'other. The innershell isof lesser diameter than theouter shell and is mounted coaxially therewith and the, spacebetween the two shells forms the water compartment of the boiler. The top of the outer shell forms the top of the boiler and the top of the water compartment. This part of the boilerisprovided with suitable connections for connectingthe boiler into a domestic heating system. The top. of the inner shell forms the crown sheetof the boiler and the bottom of the water compartmentandthe interior of the inner shell constitutes the combustion; chamber of the boiler. Ina circular opening formed inthe side walls of the shells adjacent the crown sheet of the boiler, there is mounteda flue tube heat exchanger which extends into the combustion chamber of the boiler. The heat exchanger consists of a cylindrical drum and the end pieces form tube sheets. Flue tubes extend between these tube sheets and carry the hue gases through the drum. Water openings on diametrically opposite sides of thedrum are connected to the water compartmentof the boiler, one above. the crown sheetand the other to that portion of the water compartmentbetween the, side walls of the two shells constituting thewater leg of the boiler. The heattransfer surface provided 'by' the flue tubes is additional to vthe crown sheet and the water leg'of theboiler. Heat exchan'gersof various sizes-may be, inserted in the opening through-the wall ofthe boiler, suitable packing being ,usednto, prevent the escape of flue gas aroundthe sides of the heatexchangers. ,r

M .An advantage of a boiler of thistype is the facittthatthe tube container is exposedto IJI'HzC-r: tica-llyxthe sameheat as, the tubes xandithere is an :averagetequal expansion of, the tubes andltube container. There is therefore notendency. of the tubes to buckle or their connections to the tube sheet to become loosened. l Another advantage of a boiler constructedin' this manner is the factwthat the tubes are readily accessible for repair and replacement. The heat exchanger containing the tubes may be withdrawn from the boiler for the purpose :of replacing or repairing the tubes. j

A. boiler of this type is illustrated in the accompanyingdrawingand described in detail below. Erom this illustration and detailed descripmay be had.

In the drawing:

Fig. 1 is a plan of the boiler; and

Fig. 2 is a. longitudinal, central, sectional elevation taken along the line 2-2 of Fig. 1.

The boiler illustrated in the drawing is an upright boiler suitable for a residential heating system. The boiler consists of a boiler proper including a combustion chamber and a water compartment, and a heat exchanger for providing ad-. ditional heat transfer surface. The boiler proper is mounted upon a support 1 and is made up of'.

two cylindrical shells, an outer shell 2 and an inner shell 3. The top of each of these shells is closed, the closed end of the outer shell 2''forming the top 2a of the boiler and the closed end of the inner shell 3 forming the crown sheet13a. The

inner shell is of lesser diameter than the outer shell and is mounted coaxially therewith. The space between the inner and outer shells forms the water compartment of the boiler, the space between the side walls of the shells forming the water leg of the boiler. Suitable connections are formed. in the top and side of the boiler for the purpose of connecting the boiler into a domestic heating system. Adjacent the lower end of the boiler, concentric openings through the shells 1 and 2 connected by a bushing 4 form a burner opening through which an oil burner 5 may extend. Similar concentric openings of larger diameter on the opposite side of the boiler form an explosion opening. These concentric openings in the shells 2 and 3 are connected by a tubular member 6 which protrudes beyond the edge of the boiler and hasan inclined outer end. On the upper side of this tubular member 6, there is a bracket 6a to which an explosion door '7 is pivotally mounted through a door bracket 7a, The door is so mounted that the force of gravity acting thereon tends to move it to, and normally maintain it in the closed position.

For supplying domestic hot water, a hot Water heat exchanger may be mounted in the water compartment of the boiler. To this end, in the boiler illustrated, an opening is provided in the wall of the shell 2 above the upper end of the shell 3. In this opening a bushing 8 is mounted. A hot water heat exchanger 9 which consists of a bent tube 9b and a dome head 9a through which the ends of thetube extend, is fitted in this opening in the shell 2, the flanged end of the head 9a being secured to the bushing 8 by bolts.

Theheat exchanger is mounted in the boiler above the burner opening 4 and for this purpose coaxial openings of --a diameter sufiicient to receive the heat exchanger are cut through the plates 2 and 3 adjacent the crown sheet of the boiler. The openings in these two sheets are connected together by a tubular member-10 which protrudes alittle beyond the outer shell 2. The heat exchanger consists of a cylindrical member or drum 11, the end pieces 11a and 11b of which form tube sheets. A series of flue tubes 12 are mounted within the drum andextend between the end pieces thereof. The ends of the flue tubes are expanded into openings provided therefor in the end pieces of the drum in the same manner in which flue tubes are expanded in to the ordinary tube sheet of a boiler. The'drum 11 is of a diameter slightly less than the diameter of the opening in the side wall of the boiler through which it extends. .A circumferential, external, radial flange 11c extends from the surface of the drum at a point substantially midway between the ends. The outer edge of this flange is of a diameter approximately equal to the diameter of the opening in the side wall of the boiler. When mounted in the boiler, the flange 11c together with a packing ring 10 prevents flue gases from escaping from the combustion chamber. As mounted in the boiler, substantially half of the heat exchanger extends into the combustion chamber of the boiler.

At diametrically opposite points on that portion of the drum outside of the boiler, on the upper and lower sides of the drum 11 as mounted in theboiler, there is a water opening through the side of the drum. Each of these water openings is provided with a bushing, the upper a bushing 12, and the lower a bushing 13, for the purpose of connecting suitable fittings over the openings. The bushing 12 isconnected to one end of a flanged elbow 14 which connects the upper side of the heatexchanger to an opening through the shell 2 above the crown sheet, the other end of the flanged elbow being connected to a similar bushing 15 in the opening in the shell 2. The opening in the lower side of the heat exchanger is connected, through the bushing 13 and a flanged elbow 16 having one-end secured thereto, to an opening in the portion of the shell 2 forming the wall of the water leg of the boiler, the other end of the flanged elbow being connected to the bushing 17 in the opening in the shell 2. With these connections, the circulation of the water in the boiler is from the water leg through the elbow connection 16 into the heat exchanger and from the heat exchanger through the elbow 14 and into the water compartment above the crown sheet of the boiler. I I

The outer endof the heat exchanger drum 11 is coveredby a sheet metal cylindrical member 18 which extends overthe end of the drum and ioo ios

iio

is secured thereto by a strap 19. The member water leg, there is a portion of the drum of the heat exchanger and the inner end pieceor tube sheet which is within the combustion chamber and exposed to the fire. In addition the gases resulting from the combustion pass through the flue tubes therebyv increasing the heat transfer area by this amount. The tubes and 'the'drum 11 are exposed to the same temperature conditions. Consequently, there is an average equal expansion of the tubes and the drum. This fact and the fact that the inner tube sheet is suspended within the combustion chamber provides a construction in which the tube sheet floats in accordance with the expansion and contraction of the tubes. The equal expansion and contrac tion of the drum and the movement of the'tube sheet eliminates any tendency of the tubes to buckle or to loosen in the tube sheets.

The opening through the wall of the boiler through'which theheat exchanger extends will accommodate various sized exchangers so that the boiler capacity can be varied in so far as the area of the heat transfer surface permits variation." Difierent sized packing rings 10 are'ot course used with the various heat exchangers. With this construction, the same boiler-will satisfy ice different capacity requirements and it is thus unnecessary to have a different size and design of boiler for each capacity desired.

It will be observed that the flue tubes are accessible for cleaning and for repair of replacement; the heat exchanger can be removed and. replaced with another, if necessary, while the repairs are being made.

The boiler illustrated and described has been disclosed in conjunction with an oil burner, but it is equally suitable for other fuels and other methods of firing.

It is obvious that various changes may be made by those skilled in the art in the details of the embodiment of the invention described above within the principle and scope of the invention as expressed in the appended claims.

I claim:

1. A boiler comprising, in combination, an outer shell, an inner shell of less diameter than the outer shell, the inner shell forming a combustion chamber and the space between the shells forming a water compartment above the combustion chamber, and a water leg surrounding the combustion chamber, the two shells having aligned openings through the side w'alls thereof below the water compartment, and a heat exchanger mounted in the openings through the side of the boiler including a casing extending through the opening and in to the combustion chamber and having water inlet and outlet openings through the side thereof, a tube sheet at each end of the casing, flue tubes extending between the tube sheets and secured therein, means connecting the water inlet opening of the heat exchanger to the water leg of the boiler, and means connecting the water outlet opening of the heat exchanger to the water chamber of the boiler.

2. A boiler comprising a casing forming a combustion chamber and a water compartment, a tube container structurally independent of the boiler mounted in an opening in the boiler with one end and a portion of the tube container extending into and wholly contained within the combustion chamber, the portion of the container within the combustion chamber being suspended therein, and a plurality of flue tubes extending through the tube container.

3. A boiler comprising a casing forming a combustion chamber and a water compartment, the casing having an opening through the wall of the combustion chamber section, 'a unitary heat exchanger removably mounted in theopening in the wall of the boiler with one end and a portion of the heat exchanger extending into and wholly contained within the combustion chamber, the portion of the heat exchanger within the combustion chamber being suspended therein, and means connecting the heat exchanger to the water compartment of the boiler.

4. A boiler comprising a casing forming a combustion chamber and a water compartment, the casing having an opening through the wall of the combustion chamber, a radially removable heat exchanger including a casing and flue tubes mounted in the opening in the wall of the boiler with one end a portion of the heat exchanger extending into and wholly contained within the combustion chamber, the portion of the heat exchanger within the combustion chamber being suspended therein, and means connecting the heat exchanger to the water compartment of the boiler.

5. A boiler comprising a casing forming a combustion chamber and a water compartment, the casing having an opening through the wall of the combustion chamber section, a radially removable heat exchanger mounted in the opening through the wall of the boiler casing including a casing extending through the opening and into the combustion chamber with one end and a portion of the heat exchanger casing wholly within and suspended in the combustion chamber, a tube sheet at each end of the heat exchanger casing, flue tubes extending between the tube sheets and secured therein, and means connecting the heat exchanger to the water compartment of the boiler.

HOWARD C. DAVIS.

GERTIFIGATE OF CORRECTION.

fitem Na, 1,982, 793. Decembey 4., 3934-.

HOWARD G. DAVIS.

h is hereby certified 11m enrm'v appearsjn theprinted speciiieatiml @i the abm e numbered patent. requiring correction as follows: Page 3, fines $35 and 108. ciaims 4 and 5 respectively, for "radially" read readily; am that the said Lettexrs Pmem should be read with these cm'rectimls thm'eir: that the same may cmriarm m the record of the cam in the Patent Office.

Sigma! and sealed this 12th day 0% February, A. I). 1935.

Leslie Frazer (Seal) Acting Commissioner of Patents. 

